High voltage spark gap



July 5, 1966 0. JENSEN HIGH VOLTAGE SPARK GAP 5 Sheets-Sheet 1 FiledDec. 31. 1962 i E I July 5, 1966 o. JENSEN HIGH VOLTAGE SPARK GAP 5Sheets-Sheet 2 Filed Dec. 51, 1962 ICE-.5.

INVENTOR. 0770 t/E/VJi/l/ Janene/we; 545:2, fare 39? if/Z/WM July 5,1966 o. JENSEN HIGH VOLTAGE SPARK GAP 5 Sheets-Sheet 5 Filed Dec. 31,1962 9 IN VENTOR. 2 0770 JEMfE/V fi-rreaz Eli A, FfiBEIP, fizz 46!United States Patent 3,259,792 HIGH VOLTAGE SPARK GAP Otto Jensen,Malvern, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia,Pa., a corporation of Pennsylvania Filed Dec. 31, 1962, Ser. No. 248,3683 Claims. (Cl. 315-36) My invention relates to a novel spark gap, andmore specifically relates to a spark gap in which the arc roots areconstantly moved during arcing to reduce erosion of the arcingelectrodes.

Spark gaps are well known for many electrical applications, andtypically are used to protect other equipment by arcing over toshort-circuit such equipment under predetermined conditions.

By way of example, series capacitors are commonly used in transmissionlines, and are subject to destructive voltages during the flow ofabnormally high current such as that which exists under faultconditions. A typical method for protecting such capacitors againstharmful voltages consists of the by-passing of the capacitors with afast acting switch which is, in turn, triggered by some fault sensingdevice. One form of a fast acting switch would be a calibrated spark gapwhich is in parallel with the capacitor to be protected where the gapwill spark over when the voltage across the capacitor exceeds apredetermined value.

The basic problem which is encountered during the operation of such agap is the erosion of the arcing electrodes which is produced by the arcand which will affect the calibration of the gap. In order to limit thiserosion, it is common practice to form a solid connection across the gapas soon as possible to take current flow away from the arc. However, dueto the inertia of moving parts which will be used to establish thissolid connection, there is some minimum time during which arcing mustexist and during which erosion will occur.

The principle of the present invention is to provide a magnetic field inthe arc gap area which will produce continuous motor action on the arcto thereby constantly move the location of the arc roots on the metallicsurface of the arcing electrode. Thus, the arc roots will not remain atany location long enough to cause serious burn ing or pitting of theelectrode surfaces.

In a preferred embodiment of the invention, the magnetic field thatcauses the arc to move is produced by windings located directly behindthe electrodes and connected in series with the electrodes. Thus, in theregion of the arc, the magnetic field is substantially perpendicular tothe current so that it will provide a force on the charged particlesthat form the arc to cause these particles to move perpendicular to thedirection of motion of the charged particles. When the arc gap itself isan annular member, the arc will circulate around the annular arcelectrode.

Accordingly, a primary object of this invention is to provide a novelarrangement for reducing the erosion of spark gaps.

Another object of this invention is to provide a magnetic field forcoacting with the arc current of a spark gap to cause the arc root tomove across the arcing electrode surface.

A further object of this invention is to prevent the change incalibration ofa spark gap due to erosion of the arcing surfaces.

Another object of this invention is to substantially increase the lifeof a spark gap.

These and other objects of this invention will become apparent from thefollowing description when taken in connection with the drawings, inwhich:

FIGURE 1 schematically illustrates two pairs of arc gaps constructed inaccordance with the present invention, and electrically connected forthe protection of a series capacitor.

FIGURE 2 is a cross-sectional view of an arcing electrode and itsmagnetic field generating coil which could be used in the arrangement ofFIGURE 1.

FIGURE 3 is a top view of the electrode of FIGURE 2.

FIGURE 4 illustrates an arrangement of four arcing electrodes incross-sectional view which could be used in the arrangement of FIGURE 1.

FIGURE 5 is a top plan view of the lower arcing electrode of FIGURE 4 asseen across the lines 55 in FIGURE 4.

Referring now to FIGURE 1, I have illustrated therein a capacitor 10which is connected in a line 11 which could, for example, be a highvoltage transmission line.

In order to protect the capacitor 10 by short circuiting it responsiveto predetermined fault conditions in line 11, a series connected pair ofspark gaps 12 and 13 are provided in parallel with capacitor 10. In theevent of some predetermined fault on line 11, as indicated by anincrease in voltage across capacitor 10, the spark gap will arc over andthereby short circuit the capacitor 10.

The spark gap 12, as is schematically illustrated, is formed of twoelectrodes 14 and 15, while gap 13 is formed of a similar pair ofelectrodes 16 and 17. Each of electrodes 14 through 17 are, asschematically illustrated, provided with insulated windings 18 through21 wherein the uppermost layer of winding 18 is connected directly tothe left-hand side of capacitor 10, while the beginning of winding 21 isconnected directly to the righthand side of capacitor 10. In addition,the uppermost layers of windings 19 and 20 are directly connected, asillustrated. The ends or bottom-most layers of each of windings 18through 21 are then directly connected to their respective electrodes14, 15, 16 and 17 respectively.

In order to fire gaps 12 and 13, a precision spark gap 22 is connecteddirectly across resistor 23 of the voltage dividing series resistors 23and 24 and their parallel connected voltage dividing capacitors 25 and26.

It will be noted that a further resistor 27 is provided to assure equalvoltage distribution between gaps 12 and In accordance with the presentinvention, and since' the current in coil 21 must circulate throughwinding 12 (assuming that the right-hand side of capacitor 10 ispositive with respect to the left-hand side), a magnetic field isestablished by winding 21 in the direction indicated by arrow 30.

The current path from winding 21 now continues through the arc betweenelectrodes 16 and 17, and circulates through winding 20 in a directionopposite to that of Winding 21. Therefore, winding 20 sets up a magneticfield in the direction indicated 'by arrow 31.

From like considerations, a magnetic field 32 is set up around 19 whilea magnetic field 33 is set up around winding 18.

Assuming that the arc is at the arc position 34 in spark gap 13, it isseen that the magnetic fields 30 and 31 are such that the arc 34 will becaused to rotate about the annularly shaped electrodes 16 and 17, whilein the same manner, the are 35 in gap 12 will be caused to rotatebecause of magnetic fields 32 and 33. Thus, the arc roots of arcs 34 and35 continually move around the surfaces of the are electrodes so that noone point on the surface is excessively heated and pitted. Accordingly,substantial arc erosion is prevented to thereby substantially increasethe life of the arcing electrodes and maintain a true calibration forthe arcing electrodes.

One manner in which any of the arc electrodes of FIGURE 1 may beconstructed is illustrated in FIG- URES 2 and 3.

Referring now to FIGURES 2 and 3, it will be seen the electrodes may beprovided with a support base 40 of an appropriate insulation member,while an insulation ring 41 which retains a ceramic plate 41a inprotecting arrangement with respect to the insulating base 40 receivesan annular copper ring 42 having an L-shaped cross-section.

A copper disk 43 is then secured to ring 42 by appropriate screws suchas screw 44 to complete the electrode construction. The electrode formedof disks 42 and 43 is then secured to base 41 as by a plurality of boltssuch as bolt 45 which passes through ring 41 and is threadably receivedby a tapped opening in disk 42.

Prior to assembly of disk 43 and disk 42, a winding 47 which can, forexample, have five turns which are appropriately insulated from oneanother, may be assembled in a bobbin 46 and placed about the upwardlyextending arm of L-shaped disk 42 with the disk 43 thereafter beingsecured in position to hold the winding in place.

The innermost conductor of winding 47 is then appropriately electricallyconnected directly to disk 42 in any desired manner, while the outermostconductor of winding 47 is appropriately connected to a terminal such asthe terminal 48, best shown in FIGURE 3.

With this type arrangement, it is clear that the arc current from theelectrode surface is carried through winding 47 to generate a magneticfield which surrounds the winding. Moreover, the higher the arc current,the stronger the field will be so that high current, and, therefore,destructive arcs, will be moved more quickly than low current arcs.

A second embodiment of the novel arc gap schematically illustrated inFIGURE 1 is shown in more detail in FIGURES 4 and where this embodimentdiffers from that of FIGURES 2 and 3 in that it is easier tomanufacture.

Referring now to FIGURES 4 and 5, I have illustrated therein the fourarcing electrodes 14, 15, 16 and 17, shown in FIGURE 1. Each of thearcing electrodes is provided with an insulation member such asinsulation member 60 which has an appropriate coil such as coil 61connected therein. In a similar manner, electrodes 15, 1'6 and 17 areprovided with insulation supports 62, 63

and64 which have coils 65, 66 and 67 respectively secured thereto.

Each of the supports 60, 62, 63 and 64 are further provided with cut-outsections therein, shown as cut-out section 68 for insulator 60, whichreceives a terminal structure 60 to which the inner end of coil 61 isconnee-ted.

Each of the electrodes are thenprovided with steel cover plates 70, 71,72 and 73 respectively, which are connected to the terminals such asterminal 69 of electrode 14, and are secured to insulation supports byappropriate' screws. The opposite surface of each of plates 70 through73 are then connected to the arcing electrode elements which, in'FIGURES 4 and 5, are formed of one inch diameter stainless steel pipe ortubing sections 75, 76, 77 and 78 which are welded or brazed to theirrespective plates.

It will be noted, as in FIGURE 5, that the tubes such as tu be75 arebent around to form a ring which is welded at seam 75a. 7

The upper and lower electrodes 14 and 17 are then 4 each provided withsupport sleeves 80 and 81 respectively, which could be of aluminum, by aseries of bolts in the flanges of the aluminum sleeves such as the bolts82, 83 and 84, shown for electrode 14 in FIGURE 5.

In addition, the outer end of coils 61 and 67 are electrically connectedto sleeves 80 and 81, as shown by coil end 85 of coil 61 which is takenthrough a notch 86 in plate 60, and is connected to sleeve 80 by boltssuch as bolts 87 and 88. The interior of sleeves 80 and 81 are thenthreaded to receive support bolts 90 and 91 respectively and adjustmentnuts 92 and 93 respectively. The bolts 90 and 91 are then secured toappropriate bushing structures.

With this novel arrangement, it will be understood that the axialposition of electrodes 75 and 78 can be adjusted by adjustment of nuts92 and 93.

The two centrally located electrodes 15 and 16 are each supported from acommon insulation support beam as by a series of screws such as thescrew 101 for electrode 16 and screw 102 for electrode 15.

The inner windings of windings 65 and 66 are, as was previouslydescribed, electrically connected to plates 71 and 72 respectively. Theouter ends of each of the windings 66 and 65 respectively are taken outto external terminals 105-106 and 107-108 respectively wherein theterminals 105 through 108 are all electrically connected together.

In operation, it will be understood that the first gap formed by rings75 and 76 will have its spacing adjusted by adjustment nut 92, while thespacing of the gap formed by rings 77 and 78 is controlled by adjustmentof nut 93. The operation of the system of FIGURE 4 is, of course,identical to that previously described for FIGURE 1.

Although I have described my novel invention with respect to itspreferred embodiments, many variations and modifications will now beobvious to those skilled in the art, and I prefer therefore to belimited not by the specific disclosure herein but only by the appendedclaims.

Iclaim:

1. In a high voltage spark gap comprising first and second spacedelectrodes; one of said electrodes having an extended arcing surfacedefining an extended path for the motion of an arc root; a magneticfield generating means; said magnetic field generating means beingstationarily positioned with respect to said extended arcing surface;said magnetic field generating means generating a magnetic field whichis at an angle to the direction of an are extending from any point onsaid electrode having said extended arcing surface to the other of saidfirst and second electrodes; said magnetic field generating meanscomprising an electrical winding; said electrical winding'beingconnected in series with said first and second spaced electrodes; saidelectrical winding having one terminal thereof connectedtosaid extendedarcing surface and the other terminal thereof connected to an inputterminal for said electrode having said extended arcing surface. I

2. In a high voltage spark gap comprising first and second spacedelectrodes; one of said electrodes having an extended arcing surfacedefining an extended path for the motion of an arc root; a magneticfield generating means; said magnetic field generating means beingstationarily positioned with respect to said extended arcing surface;said magnetic field generating means generating a magnetic field whichis at an angle to the direction of an are extending from any point onsaid electrode having said extended arcing surface to the other of saidfirst and second electrodes; said extended arcing surface having a diskshape; said magnetic field generating means comprising an electricalwinding; said electrical winding being connected in series with saidfirst and second spaced electrodes; said electrical winding having oneterminal thereof connected to said extended arcing surface and the otherterminal thereof connected to an input terminal for said electrodehaving said extended arcing surface.

3. In a high voltage spark gap comprising first and second spacedelectrodes; one of said electrodes having an extended. arcing surfacedefining an extended path for the motion of an arc root; a magneticfield generating means; said magnetic field generating means beingst-ati'onarily positioned with respect to said extended arcing surface;said magnetic field generating means generating a magnetic field whichis at an angle to the direction of an are extending from any point onsaid electrode having said extended arcing surface to the other of saidfirst and second electrodes; said extended arcing surface having a diskshape; said magnetic field generating means comprising an electricalwinding; said electrical winding being connected in series with saidfirst and second spaced electrodes; said electrical winding having oneterminal thereof connected to said extended arcing surface and the otherterminal thereof connected to an input terminal for said electrodehaving said extended arcing surface; said winding being coaxial withsaid disk-shaped extending surface.

References Cited by the Examiner DAVID J. GALVIN, Primary Examiner.

ROBERT SEGAL, GEORGE N. WESTBY, Examiners.

D. E. SRAGOW, Assistant Examiner.

1. IN A HIGH VOLTAGE SPARK GAP COMPRISING FIRST AND SECOND SPACEDELECTRODES; ONE OF SAID ELECTRODES HAVING AN EXTENDED ARCING SURFACEDEFINING AN EXTENDED PATH FOR THE MOTION OF AN ARC ROOT; A MAGNETICFIELD GENERATING MEANS; SAID MAGNETIC FIELD GENERATING MEANS BEINGSTATIONARILY POSITIONED WITH RESPECT TO SAID EXTENDED ARCING SURFACE;SAID MAGNETIC FIELD GENERATING MEANS GENERATING A MAGNETIC FIELD WHICHIS AT AN ANGLE TO THE DIRECTION OF AN ARC EXTENDING FROM ANY POINT ONSAID ELECTRODE HAVING SAID EXTENDED ARCING SURFACE TO THE OTHER OF SAIDFIRST AND SECOND ELECTRODES; SAID MAGNETIC FIELD GENERATING MEANSCOMPRISING AN ELECTRICAL WINDING; SAID ELECTRICAL WINDING BEINGCONNECTED IN SERIES WITH SAID FIRST AND SECOND SPACED ELECTRODES; SAIDELECTRICAL WINDING HAVING ONE TERMINAL THEREOF CONNECTED TO SAIDEXTENDED ARCING SURFACE AND THE OTHER TERMINAL THEREOF CONNECTED TO ANINPUT TERMINAL FOR SAID ELECTRODE HAVING SAID EXTENDED ARCING SURFACE.